Properties required of a waterproofing material used as a coating material for waterproofing the surface of concrete, mortar, or the like used in constructions such as roofs, verandas, parking lots, corridors, and swimming pools include resistance against vibrations of buildings and impact caused by fallen objects, capability of sealing the surface of a crack formed in the concrete or mortar beneath the coat, alkali-resistance, and high adhesion to the substrate.
Conventionally, asphalt and urethane resins have been used as waterproof lining materials for concrete and mortar but have been unsatisfactory. Recently, there has often been employed the FRP method, in which unsaturated polyester resin or vinyl ester resin which are endowed with pliability is combined with a fibrous reinforcing material.
Thermosetting resins used in the FRP method have been studied energetically in recent years, and there have been proposed various types of thermosetting resins such as those which are endowed with both flexibility and chemical resistance, those which exhibit a large % elongation at low temperature, and those which are endowed with air drying property, as described in Japanese Patent Application Laid-Open (kokai) Nos. 8-319328, 1-201362, 8-311805, 5-295862, 1-96079, 4-253717, and 4-142323.
When lining is performed by use of unsaturated polyester resin or vinyl ester resin, room temperature setting by use of a peroxide serving as a catalyst is normally employed. However, the room temperature setting has a drawback that it requires a step for impregnating a fibrous reinforcing material layer with a resin. Also, a long period of time is required before the resin is completely set, which leads to both decrease in working efficiency and volatilization of reactive monomers such as styrene monomers, resulting in a deteriorated resin performance due to a change in the ratio of the resin compositions, loss of resin in amount, and air pollution at the work site. Moreover, there are required intricate procedures such as measuring a peroxide serving as a catalyst with a dropping pipet and mixing it with resin at the working site. In addition, since gelation time of resin itself varies significantly with temperature, adjustment of the amount of a catalyst to be used is difficult, and failure in adjustment leads to unsuccessful adjustment of pot life of the resin.
As one means to solve these drawbacks, volatile monomers, such as styrene, contained in the resin are replaced by high-boiling-point compounds, to thereby manage the problems of air pollution and odor in the workplace. However, there remain unsolved such drawbacks involved in the system in which a peroxide catalyst is used in combination with an ambient-temperature-setting resin as in the case of unsaturated polyester resin or vinyl ester resin, which requires a long period of time for the resin to be set. Also remaining are problems that use of a peroxide as a catalyst might be hazardous, that complicated procedures are required for the addition of the peroxide as a catalyst, and that the adjustment of pot life of the resin is difficult.
There may be suggested use of a prepreg sheet that has been obtained by B-staging (prepregnating) glass fiber or similar material impregnated with an unsaturated polyester resin or a vinyl ester resin so as to achieve a hardness that allows easy handling. In this connection, room temperature setting type prepreg sheets is not usable because they can be stored for only a short period. With regard to photocurable prepreg sheets, conventional methods for prepregnating thermosetting resins--or example, metal thickening of unsaturated polyester resin by use of magnesium oxide and isocyanate thickening of vinyl ester resin--are unable to keep photocurable stable prepreg sheets. In addition, there are drawbacks that, since a reactive diluent such as a styrene monomar contained in the resin does not participate in the thickening reaction of vinyl ester resin or that of unsaturated polyester resin, resin volatilizes or escapes from the fibrous substrate during storage of the prepreg sheet.
In a conventional wet FRP-waterproofing method, a buffer layer comprised of a soft resin alone is often formed beneath the FRP lining layer so that the lining layer can seal the surface of a crack formed in the concrete. However, conventional metal thickening by use of magnesium oxide and isocyanate thickening require a long time before completion of reaction, with the result that the buffer layer and the fiber-reinforced layer are intermixed, leading to difficulty in forming a definite buffer layer. Thus, manufacture of photocurable prepreg sheets applicable to an FRP lining layer having a buffer layer thereon has been difficult.